1. Field of the Invention
The present invention relates to resistance temperature sensing devices, but in particular to metal film, positive temperature coefficient of resistance (TCR) temperature sensing devices.
2. Description of the Prior Art
Various resistance temperature sensing devices such as thermisters, PN junction transistors, wire wound resistors, and the like have been known in the prior art, but each of such prior art devices has numerous disadvantages thereby rendering it generally unsuitable for wide scale application. For example, thermisters have poor thermal stability as well as poor repeatability. In general thermisters are relatively expensive and have a negative temperature coefficient of resistance. Similarly, PN junction transistors have poor repeatability and a negative temperature coefficient of resistance. Wire wound resistors, on the other hand, have an undesirably high change in resistance due to mechanical vibration and poor thermal stability. Such wire wound resistors also are relatively expensive. In addition to such disadvantages, thermisters do not have a linear response nor a relatively linear response. Furthermore, the construction of certain of the prior art temperature sensing devices requires costly equipment and complicated assembly work.